Delivery unit

ABSTRACT

Delivery units are already known, having a drive rotor and an output rotor driven by the drive rotor, which are rotatably mounted in a rotor housing and interact in a meshing manner via spur toothing in each case, at least one of the two rotors being axially adjustable and, on the rear side thereof, facing away from the other rotor, having a compensating pressure applied via a compensation channel. The compensating pressure acts firstly counter to the axial compressive forces which arise in the working chambers formed between the rotors, and secondly compensates for the forces which would force the two rotors apart. This ensures that the distance between the rotors does not change. The compensating pressure frequently corresponds to the pressure on the pressure side of the delivery unit, which means that the forces on the rotors are considerably higher than necessary. This leads to increased friction in the bearings and between the rotors. The rear side of the rotors can also be supplied via slot flows. This has the disadvantage that an undefined compensating pressure is established, which depends on the leakage flows which flow into the space or out of the space behind the rotor. In addition, in this embodiment the compensating pressure does not have the ideal value for low-friction operation. In the delivery unit according to the invention, a defined compensating pressure is established on the rear side of the axially adjustable rotors. The invention provides for a control valve ( 14 ) to be provided, which sets the compensating pressure to a predetermined value between a pressure on the pressure side and a pressure on the suction side.

BACKGROUND OF THE INVENTION

The invention proceeds from a conveying assembly.

A conveying assembly is already known from DE 103 35 939 A1, with a driving rotor and with a driven rotor driven by the driving rotor, said rotors being mounted rotatably in a rotor housing and cooperating in a meshing manner in each case via a spur toothing, at least one of the two rotors being axially adjustable and being acted upon, on its rear side facing away from the other rotor, by a compensating pressure via a compensating duct. The compensating pressure, on the one hand, counteracts the axial pressure forces which arise in the working chambers formed between the rotors and, on the other hand, compensates forces which would press the two rotors apart from one another. This ensures that the spacing between the rotors is not changed. The compensating pressure often corresponds to the pressure on the delivery side of the conveying assembly, and therefore the forces upon the rotors are markedly higher than necessary. This leads to increased friction in the bearings and between the rotors. The rear side of the rotors may also be supplied via gap flows. The disadvantage of this is that an undefined compensating pressure is established which is dependent on the leakage streams flowing into the space or out of the space behind the rotor. In this version, too, the compensating pressure does not have the ideal value for low-friction operation.

SUMMARY OF THE INVENTION

By contrast, the advantage of the conveying assembly according to the invention, is that a defined compensating pressure is set on the rear side of the axially adjustable rotor, in that a control valve is provided which sets the compensating pressure at a predetermined value between a pressure on the delivery side and a pressure on the suction side. The compensating pressure is set as a function of the respective operating component of the conveying assembly, specifically at a value which enables the conveying assembly to operate with the lowest friction possible.

Via the pressure, set in this way, upon the rear face of the rotor, a defined force is exerted upon the rotor. The pressure on the suction side and that on the delivery side exert upon the rotors forces which attempt to drive the rotors apart from one another. Since the pressure-loaded faces remain the same, the ideal compensating force upon the rotors is proportional to the pressure difference between the delivery side and suction side. A proportional valve is therefore highly suitable for compensating the forces and therefore for reducing the friction between the rotors, between the rotors and housing and in the bearings. This leads to lower wear and higher efficiency. The compensating pressure may be used with a compensating effect both on one rotor and on both rotors. Furthermore, different compensating pressures may be generated for the two rotors by the use of two proportional valves.

According to an advantageous version, the control valve has a control piston and three control chambers separated from one another via the control piston, the first control chamber of the control valve being acted upon by the pressure on the delivery side and the second control chamber by the pressure on the suction side, the third control chamber being flow-connectable to the first chamber or to the second chamber via a control duct formed on the control piston. A compensating pressure is thus set which has a value between a pressure on the delivery side and a pressure on the suction side.

It is especially advantageous if the inlet cross section of the control duct is variable as a function of the position of the control piston, since a predetermined pressure loss is thereby achieved.

It is advantageous, furthermore, if the control piston projects through a passage duct between the first and the second chamber, the variable inlet cross section of the control valve being achieved by means of a partial overlap of the inlet cross section by the wall of the passage duct. A predetermined pressure loss of the control valve is thereby generated.

It is highly advantageous if the control valve is a proportional valve in which the quotient of the difference between the compensating pressure and suction pressure and the difference between the delivery-side pressure and suction pressure is constant.

It is also advantageous if the control piston is acted upon by two valve springs counteracting one another, since a return of the control piston into a predetermined initial position when the conveying assembly is switched off is thereby achieved.

It is advantageous, furthermore, if the control valve is fastened to the rotor housing of the conveying assembly or is integrated in the rotor housing.

Moreover, it is advantageous that the pressure of the third control chamber is conducted via a flow connection onto the rear side of the axially adjustable rotor, since the compensating pressure set at the control valve thereby arrives on the rear side of the rotor.

BRIEF DESCRIPTION OF THE DRAWING

An exemplary embodiment of the invention is illustrated in simplified form in the drawing and is explained in more detail in the following description.

DETAILED DESCRIPTION

The drawing shows in section a part view of the conveying assembly according to the invention.

The conveying assembly serves for the conveyance of liquid or gaseous media, for example liquids or gases. The conveying assembly 1 has a driving rotor 2 and a driven rotor 3 driven by the driving rotor 2, the two rotors being arranged rotatably in a rotor housing 4 and cooperating in a meshing manner in each case via a spur toothing 5. The spur toothing 5 is, for example, a cycloidal or trochoidal toothing, but may, of course, also be another toothing. According to the exemplary embodiment, the two rotors 2, 3 have partially a spherical shape on their outer circumference. The driving rotor 2 is driven by a motor 8, for example an electric motor. A rotor bearing 9, 10 is provided in each case for the rotors 2, 3. The rotors 2, 3 have in each case a rotor axis 6, 7, said rotor axes being, for example, inclined with respect to one another, that is to say not in alignment. At least one of the two rotors 2, 3 is axially adjustable. For example, this axially adjustable rotor 3 is pressed in the direction of the other rotor 2 by means of a spring element 30. The spring element 30 is a compression spring, for example a disk spring or a helical spring. This ensures that the rotors 2, 3 bear one against the other at all times.

For example, provision is made for the two rotors 2, 3 to be axially adjustable in their rotor bearing 9, 10. Between the rotors 2, 3, working spaces 11 are formed, in which the medium is conveyed by positive displacement. Pressure is built up in working spaces 11, the volume of which has just been reduced. This pressure also acts in the axial direction upon the rotor bearings 9, 10 of the rotors 2, 3. In order to prevent the rotors 2, 3 from being lifted off, the rear side 2.1, 3.1, facing away from the other rotor 2, 3 in each case, of the rotor 2, 3 is acted upon by a compensating pressure. The pressure forces acting upon the rotors 2, 3 are thereby at least partially compensated. According to the exemplary embodiment, this takes place on both rotors 2, 3, but may, of course, also be implemented on only one of the rotors 2, 3.

According to the invention, a control valve 14 is provided which sets the compensating pressure acting upon the rear sides 2.1, 3.1 at a predetermined value between a pressure on the delivery side and a pressure on the suction side. The suction side is an inlet, not illustrated, and the delivery side an outlet, not illustrated, of the conveying assembly. The compensating pressure is thus set at a predetermined value as a function of the respective operating point of the conveying assembly, specifically at a value which enables the conveying assembly to be operated with the lowest friction possible.

The control valve 14 has a control piston 15 and three control chambers 16, 17, 18 separated from one another via the control piston 15, the first control chamber 16 of the control valve 14 being acted upon by the pressure on the delivery side and the second control chamber 17 by the pressure on the suction side, the third control chamber 18 being flow-connectable to the first control chamber 16 or to the second control chamber 17 via a control duct 19 formed on the control piston 15. The control duct 19 runs in the direction of the longitudinal extent of the control piston 15.

An inlet cross section 20 into the control duct 19 is variable as a function of the position of the control piston 15. The inlet cross section is formed by at least one inlet port into the control duct 19. For example, a plurality of inlet ports are formed on the circumference of the control piston 15. The control piston 15 projects through a passage duct 22 between the first 16 and the second 17 control chamber, the variable inlet cross section of the control valve 14 being achieved by means of a partial overlap of the inlet cross section by the wall of the passage duct 22. The control duct 19 issues at its end facing away from the inlet cross section 20 into the third control chamber 18. The pressure of the third control chamber 18 is conducted via a flow duct 24 onto the rear side 2.1, 3.1 of the rotors 2, 3.

The control valve 14 may be fastened to the rotor housing 4 of the conveying assembly or be integrated in the rotor housing 4. The control valve 14 has two inlets 26, 27 for connection to the suction side and to the delivery side of the conveying assembly respectively and an outlet 28 for connection to the flow duct 24 leading to the rear side 2.1, 3.1 of the rotors 2, 3.

The control valve 14 is designed, for example, as a proportional valve. The control piston 15 is acted upon, for example, by two valve springs 23 counteracting one another, so as to ensure return into the initial position. 

1. A conveying assembly with a driving rotor (3) and with a driven rotor (3) driven by the driving rotor (2), said rotors being mounted rotatably in a rotor housing (4) and cooperating in a meshing manner in each case via a spur toothing (5), at least one of the two rotors (2, 3) being axially adjustable and being acted upon, on a rear side (2.1, 3.1) facing away from the other rotor (2, 3), by a compensating pressure, characterized in that a control valve (14) sets the compensating pressure at a predetermined value between a pressure on a delivery side and a pressure on a suction side.
 2. The conveying assembly as claimed in claim 1, characterized in that the control valve (14) has a control piston (15) and first, second and third control chambers (16, 17, 18) separated from one another via the control piston (15), the first control chamber (16) of the control valve (14) being acted upon by the pressure on the delivery side and the second control chamber (17) by the pressure on the suction side, the third control chamber (18) being flow-connectable to the first control chamber (16) or to the second control chamber (17) via a control duct (19) formed on the control piston (15).
 3. The conveying assembly as claimed in claim 2, characterized in that an inlet cross section of the control duct (19) is variable as a function of the position of a control piston (15).
 4. The conveying assembly as claimed in claim 3, characterized in that the control piston (15) projects through a passage duct (22) between the first and the second control chamber (16, 17), the variable inlet cross section of the control valve (14) being achieved by a partial overlap of the inlet cross section by a wall of the passage duct (22).
 5. The conveying assembly as claimed in claim 1, characterized in that the control duct (19) issues at an end facing away from the inlet cross section into the third control chamber (18).
 6. The conveying assembly as claimed in claim 1, characterized in that the control valve (14) is a proportional valve.
 7. The conveying assembly as claimed in claim 1, characterized in that the control piston (15) is acted upon by two valve springs (23) counteracting one another.
 8. The conveying assembly as claimed in claim 1, characterized in that the control valve (14) is fastened to the rotor housing (4) of the conveying assembly.
 9. The conveying assembly as claimed in claim 1, characterized in that a pressure of the third control chamber (18) is conducted via a flow connection (24) onto a rear side (2.1, 3.1) of the rotors (2, 3).
 10. The conveying assembly as claimed in claim 1, characterized in that the driving rotor (2) and the driven rotor (3) have a cycloidal toothing.
 11. The conveying assembly as claimed in claim 1, characterized in that the control valve (14) is integrated in the rotor housing (4).
 12. The conveying assembly as claimed in claim 1, characterized in that the driving rotor (2) and the driven rotor (3) have a trochoidal toothing. 